Edited picture-setting to new color
The issue is that your mask is not the correct size for your image, and you need to change the Mix Node settings from &quot;Color&quot; to &quot;Mix&quot;.
You need to change the settings for your mask node to &quot;Fixed&quot; instead of &quot;Scene Size.&quot;  Then, type in the x/y dimensions of your image.  I also changed the mix node to &quot;Mix&quot; instead of &quot;Color.&quot;

If you don't know how to find the dimension of your image, open it on Windows Explorer, right-click on it, and press &quot;Properties.&quot;  You can find the dimensions under the &quot;Details&quot; tab.
Hope that fixes your problem!  Let me know if you have any other issues.